Preparation method of modified grinding aid for reducing cement particle hardness and application thereof

Abstract

The application relates to the field of cement building materials, and particularly discloses a preparation method of a modified grinding aid for reducing the hardness of cement particles and application thereof, which comprises the following steps: (1) adding 5-hydroxy-2-nitrobenzoic acid into water to form a dispersion liquid, then adding an alkali liquor to adjust the pH value of the dispersion liquid, and then adding a rare earth compound aqueous solution under stirring, heating and reacting to obtain a rare earth ion and 5-hydroxy-2-nitrobenzoic acid chelate reaction liquid; (2) cooling the chelate reaction liquid, adding a polycarboxylic acid water reducing agent, and then stirring and reacting to obtain a ternary coordination complex reaction liquid; and (3) cooling the ternary coordination complex reaction liquid to room temperature, adding an organic substance containing a coordination functional group, stirring and reacting, adding a polycarboxylic acid water reducing agent, uniformly mixing, diluting the obtained system with water, and obtaining the product. The ternary coordination complex grinding aid system can significantly reduce the hardness of cement clinker particles and greatly improve the grinding efficiency.

Description

Technical Field

[0001] This invention relates to the field of cement building materials, specifically to a method for preparing a modified grinding aid that reduces the hardness of cement particles and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In cement production, the grinding process is extremely energy-intensive, accounting for approximately 60-70% of the total electricity consumption. Furthermore, ball mills have very low energy utilization rates, with over 90% of the input energy dissipated as heat, leaving less than 1% of the energy actually used for material crushing. Therefore, adding grinding aids to improve the grinding efficiency of cement clinker and reduce unit product electricity consumption is one of the most direct and effective technical approaches to achieving energy conservation and emission reduction in the cement industry. Currently, cement grinding aids mainly utilize alkanolamines (such as triethanolamine and triisopropanolamine), polyols (such as ethylene glycol and glycerol), and industrial byproducts (such as lignin sulfonates). These grinding aids primarily improve grinding efficiency by reducing particle surface energy and minimizing micro-powder agglomeration; however, they inherently lack the ability to reduce the hardness of the cement clinker particles themselves, resulting in a significant upper limit to their grinding efficiency. Typically, they can only increase the hourly output of the ball mill by 5-10%.

[0004] Polycarboxylate superplasticizers (PCEs), as a new generation of high-performance superplasticizers, possess excellent dispersing ability due to their comb-like molecular structure, effectively preventing the re-aggregation of fine powders during grinding. In recent years, researchers have begun exploring the application of PCE in the field of grinding aids. Studies have shown that PCE-type grinding aids can improve cement particle size distribution and, to some extent, increase grinding efficiency. However, PCE molecules mainly act on the particle surface and cannot interfere with the mechanical strength of the cement clinker particles themselves. The grinding aid effect still mainly relies on surface physicochemical interactions, making it difficult to fundamentally reduce the hardness or brittleness of clinker particles. This results in limited yield increases when grinding high-hardness, low-grindability clinker (typically only maintaining between 10-15%). Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing a modified grinding aid that reduces the hardness of cement particles and its application. This method, through a ternary coordination complex grinding aid system, can significantly reduce the hardness of cement clinker particles and substantially improve grinding efficiency. Specifically, the technical solution of this invention is as follows.

[0006] First, this invention discloses a method for preparing a modified grinding aid that reduces the hardness of cement particles, comprising the following steps: (1) Add 5-hydroxy-2-nitrobenzoic acid to water to form a dispersion, then add alkali solution to adjust the pH value of the dispersion, and then add rare earth compound aqueous solution under stirring. After completion, heat the reaction to obtain rare earth ions and 5-hydroxy-2-nitrobenzoic acid chelate reaction solution for later use.

[0007] (2) After cooling the chelate reaction solution, add the polycarboxylate superplasticizer, and then stir the reaction. After completion, PCE-5-hydroxy-2-nitrobenzoic acid-RE is obtained. 3+ Ternary coordination complex reaction solution, ready for use.

[0008] (3) After cooling the ternary coordination complex reaction solution to room temperature, add an organic compound containing at least two coordination functional groups to it, and then stir the reaction. After completion, add polycarboxylate superplasticizer and mix well, then dilute the resulting system with water to obtain the modified grinding aid.

[0009] Further, in step (1), the mass ratio of 5-hydroxy-2-nitrobenzoic acid (C7H5NO5) to water is 1:70~85.

[0010] Further, in step (1), the pH value of the dispersion is adjusted to 4-5.5. Optionally, the alkaline solution includes at least one of the following: sodium hydroxide solution, potassium hydroxide solution, ammonia water, sodium carbonate solution, sodium bicarbonate solution, etc.

[0011] Further, in step (1), the molar ratio of the rare earth compound to 5-hydroxy-2-nitrobenzoic acid is 1:1~2.

[0012] Further, in step (1), the rare earth compound includes at least one of the following: nitrates or chlorides of lanthanum, cerium, praseodymium, neodymium, and yttrium. The rare earth compound has an empty 4f or 5d orbital, which accepts lone pairs of electrons provided by the phenolic hydroxyl oxygen and carboxyl oxygen of the 5-hydroxy-2-nitrobenzoic acid to form a coordinate bond, thereby obtaining a chelate of the rare earth ion and 5-hydroxy-2-nitrobenzoic acid. At the same time, the benzene ring of the 5-hydroxy-2-nitrobenzoic acid has both a phenolic hydroxyl (-OH) and a nitro (-NO2) substituent (its structural formula is shown in formula (1) below). The nitro group can regulate its coordination activity with the rare earth ion by reducing the electron cloud density of the phenolic hydroxyl oxygen atom through electron-withdrawing conjugation and inductive effects, so that the 5-hydroxy-2-nitrobenzoic acid and the rare earth ion form a chelate with moderate stability.

[0013] ; Equation (1).

[0014] Further, in step (1), the heating reaction temperature is 60~80℃, and the time is 30~60min. In this process, the present invention utilizes the deprotonated phenolic hydroxyl (-OH) and carboxyl (-COOH) groups on the 5-hydroxy-2-nitrobenzoic acid molecule as electron pair donors, and rare earth ions (RE) as electron pair acceptors. 3+ A coordination reaction occurs, generating a stable rare earth ion chelate with 5-hydroxy-2-nitrobenzoic acid.

[0015] Further, in step (2), the chelate reaction solution is cooled to 40~50°C.

[0016] Further, in step (2), the mass ratio of the polycarboxylate superplasticizer to 5-hydroxy-2-nitrobenzoic acid is 5~18:0.3~2.

[0017] Further, in step (2), the temperature of the stirring reaction is 40~50℃, the stirring rate is 200~400r / min, and the reaction time is 30~60min. During this process, the uncoordinated phenolic hydroxyl groups (-OH) and carboxyl groups (-COOH) on the chelate form intermolecular hydrogen bonds with the carboxyl groups (-COOH) on the polycarboxylate superplasticizer (PCE) molecular chain to achieve site anchoring, forming the stable PCE-5-hydroxy-2-nitrobenzoic acid-RE. 3+ Ternary coordination complexes.

[0018] Further, in step (3), the mass ratio of the organic compound to 5-hydroxy-2-nitrobenzoic acid is 1:0.2~1.5.

[0019] Further, in step (3), the coordinating functional group includes: carboxyl group, ortho-phenolic hydroxyl group, phosphonic acid group, etc. Optionally, the organic compound providing the above-mentioned coordinating functional group includes at least one of: protocatechuic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 3,4-dihydroxyphenylacetic acid, etc.

[0020] Further, in step (3), the stirring reaction time is 20-40 min, and the stirring rate is 150-300 r / min. During this process, the coordinating functional groups of the organic matter form non-covalent interactions such as hydrogen bonds, electrostatic interactions, or π-π stacking with the polar functional groups (such as ether bonds, uncoordinated carboxyl groups, etc.) exposed on the surface of the ternary coordination complex. Under thermodynamic drive, a functional reinforcing network is formed by self-assembly around the ternary coordination complex.

[0021] Further, in step (3), the mass ratio of the polycarboxylate superplasticizer to 5-hydroxy-2-nitrobenzoic acid is 5~12:0.3~2.

[0022] Further, in step (3), 95 to 105 times the mass of water is added to the system for dilution.

[0023] Secondly, this invention discloses the application of the modified grinding aid in the preparation of cement clinker powder, comprising the following steps: mixing the modified grinding aid with cement clinker and then grinding the mixture to obtain cement clinker powder. Optionally, the modified grinding aid is 0.1~0.5% of the mass of the cement clinker.

[0024] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: This invention employs 5-hydroxy-2-nitrobenzoic acid, rare earth ions, polycarboxylate superplasticizer, and an organic compound containing at least two coordinating functional groups to construct a ternary coordination complex grinding aid. Through the chelation coordination of rare earth ions with 5-hydroxy-2-nitrobenzoic acid, and the anchoring effect of this chelate with the carboxyl groups on the PCE molecular chain, the rare earth ions are stably fixed onto the PCE molecule. During the grinding process, this grinding aid can target and deliver rare earth ions to the tips of microcracks on the surface of cement clinker particles. The lattice distortion effect of the rare earth ions significantly reduces particle hardness, thereby greatly improving grinding efficiency. This is because, on the one hand, when grinding cement clinker, the grinding aid utilizes its PCE segments to preferentially adsorb onto high-energy active sites and newly formed microcracks on the surface of cement clinker particles. The rare earth-5-hydroxy-2-nitrobenzoic acid complex anchored on the PCE chain is then "targeted" and delivered to these crack tips. Under the unique mechanochemical coupling environment at the crack tip, the complex structure in the grinding aid gradually dissociates, releasing rare earth ions that penetrate into the mineral lattice. This utilizes the lattice distortion and chemical bond weakening effects induced by rare earth ion doping to reduce the fracture energy barrier of cement clinker particles at the atomic scale. Simultaneously, the biomimetic hydration layer formed on the particle surface by the organic matter containing coordination functional groups in the peripheral reinforcement network significantly reduces frictional resistance and improves grinding efficiency. Furthermore, because the rare earth ions entering the cement clinker particles reduce the difficulty of crack propagation, PCE molecules can penetrate deeper into the surface of newly formed nanoscale cracks to exert an immediate dispersion effect. At the same time, the coordination functional groups in the peripheral reinforcement network capture the Ca exposed on the surface of new cracks. 2+ And Al 3+ The presence of impurity ions prevents them from re-crosslinking and causing secondary particle agglomeration, ensuring the continuous and efficient positive cycle of "weakening → crushing → dispersing → re-weakening". Furthermore, the PCE in the grinding aid of this invention has natural and good compatibility with the PCE water-reducing agent added to cement concrete materials. The biomimetic hydration layer formed on the surface of cement clinker particles by the peripheral reinforcing network helps improve the workability retention of the cement concrete slurry, effectively reducing slump loss and overcoming the industry-wide problem of poor compatibility between traditional amine grinding aids and water-reducing agents. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention and do not constitute an undue limitation of the invention.

[0026] Figure 1 The image shows a sample of the modified grinding aid prepared in Example 1 below.

[0027] Figure 2 The image shows a sample of the modified grinding aid prepared in Example 2 below.

[0028] Figure 3 The image shows a sample of the modified grinding aid prepared in Example 3 below.

[0029] Figure 4 The image shows a sample of the modified grinding aid prepared in Example 4 below.

[0030] Figure 5 The image shows a sample of the modified grinding aid prepared in Example 5 below.

[0031] Figure 6 The image shows a sample of the modified grinding aid prepared in Example 6 below.

[0032] Figure 7 The image shows a sample of the modified grinding aid prepared in Example 7 below. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the invention. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as those skilled in the art. The preferred embodiments and materials described in this invention are for illustrative purposes only. The technical solutions of the present invention will now be further described with reference to specific embodiments.

[0034] Example 1: A method for preparing a modified grinding aid to reduce the hardness of cement particles, comprising the following steps: (1) 5-Hydroxy-2-nitrobenzoic acid and water were mixed at a mass ratio of 1:80 and stirred to form a dispersion. Then, 0.1 mol / L NaOH solution was added to adjust the pH of the suspension to 5. The resulting system was then placed under a nitrogen protective atmosphere, and a 6.25% lanthanum nitrate solution was added dropwise to the system under stirring at a molar ratio of rare earth compound (lanthanum nitrate) to 5-hydroxy-2-nitrobenzoic acid of 1:2. After the addition was complete, the system was heated to 70°C and reacted at a constant temperature for 45 min to obtain a chelate reaction solution of rare earth ions and 5-hydroxy-2-nitrobenzoic acid, which was then set aside.

[0035] (2) The chelate reaction solution was cooled to 45°C and kept at that temperature. Then, a polycarboxylate superplasticizer was added to it, with a mass ratio of 18:0.5 between the superplasticizer and the 5-hydroxy-2-nitrobenzoic acid. The mixture was then stirred at 300 r / min for 45 min at the 45°C temperature to obtain PCE-5-hydroxy-2-nitrobenzoic acid-RE. 3+ Ternary coordination complex reaction solution, ready for use.

[0036] (3) After cooling the ternary coordination complex reaction solution to room temperature, 3,4-dihydroxyphenylacetic acid is added to it, with a mass ratio of 3,4-dihydroxyphenylacetic acid to 5-hydroxy-2-nitrobenzoic acid of 1:0.8. Then, the mixture is stirred at 200 r / min for 30 min. After the reaction is complete, polycarboxylate superplasticizer is added again, with a mass ratio of 3,4-dihydroxyphenylacetic acid to 5-hydroxy-2-nitrobenzoic acid of 9:1. Finally, 100 times the mass of water is added to the obtained system for dilution, and the mixture is stirred evenly to obtain the modified grinding aid (e.g., Figure 1 (As shown).

[0037] Performance Testing: 1. The hardness of cement clinker particles before and after treatment with the grinding aid was tested using a micro Vickers hardness tester. The method was as follows: the silicate cement clinker was crushed and screened into blocks with a diameter of 20-30 mm. These blocks were used as a control group, and the average Vickers hardness of the block profile was tested using a micro Vickers hardness tester (load 100g, holding pressure 15s). Then, another block was immersed in the grinding aid of this embodiment for 2 hours, removed, and dried at 60℃. The average Vickers hardness was then tested using the same method, and the hardness reduction rate relative to the control group was calculated. 2. Grinding tests were conducted using a standard laboratory ball mill (Ф500mm×500mm). 5% (by weight) of natural dihydrate gypsum was added to the silicate cement clinker, followed by 0.1% (by weight) of the grinding aid from this embodiment (experimental group). The control group consisted of silicate cement clinker without the added grinding aid. The grinding time required to achieve the same specific surface area (350±5m² / kg) was measured, and the time saving rate of the experimental group relative to the control group was calculated to test the grinding efficiency. 3. The slump loss of ordinary silicate cement clinker with 0.35% (by weight) of the modified grinding aid from this embodiment added was tested according to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures". The test results for the above performance indicators are shown in Table 1 below.

[0038] Table 1

[0039] Example 2: A method for preparing a modified grinding aid to reduce the hardness of cement particles, comprising the following steps: (1) 5-Hydroxy-2-nitrobenzoic acid and water were mixed at a mass ratio of 1:70 and stirred to form a dispersion. Then, 0.1 mol / L NaOH solution was added to adjust the pH of the suspension to 4. The resulting system was then placed under a nitrogen protective atmosphere, and 10% cerium nitrate solution was added dropwise to the system under stirring at a molar ratio of rare earth compound (cerium nitrate) to 5-hydroxy-2-nitrobenzoic acid of 1:1.5. After the addition was complete, the system was heated to 60°C and reacted at a constant temperature for 60 min to obtain a chelate reaction solution of rare earth ions and 5-hydroxy-2-nitrobenzoic acid, which was then set aside.

[0040] (2) The chelate reaction solution was cooled to 40°C and kept at that temperature. Then, a polycarboxylate superplasticizer was added to it, with a mass ratio of 5-hydroxy-2-nitrobenzoic acid to 5:0.3. The mixture was then stirred at 400 r / min for 30 min at the 40°C temperature to obtain PCE-5-hydroxy-2-nitrobenzoic acid-RE. 3+ Ternary coordination complex reaction solution, ready for use.

[0041] (3) After cooling the ternary coordination complex reaction solution to room temperature, a coordinating organic compound (composed of protocatechuic acid and 3,4-dihydroxyphenylacetic acid in a mass ratio of 1:2) is added to it, with a mass ratio of 1:0.2 to the 5-hydroxy-2-nitrobenzoic acid. The mixture is then stirred at 300 r / min for 20 min. After this, a polycarboxylate superplasticizer is added again, with a mass ratio of 5:0.3 to the 5-hydroxy-2-nitrobenzoic acid. Finally, 95 times its mass of water is added to the resulting system for dilution, and the mixture is stirred until homogeneous to obtain the modified grinding aid (e.g., ...). Figure 2 (As shown).

[0042] Performance testing: The modified grinding aid prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in Table 2 below.

[0043] Table 2

[0044] Example 3: A method for preparing a modified grinding aid to reduce the hardness of cement particles, comprising the following steps: (1) 5-Hydroxy-2-nitrobenzoic acid and water were mixed at a mass ratio of 1:85 and stirred to form a dispersion. Then, 0.1 mol / L NaOH solution was added to adjust the pH of the suspension to 5.5. The resulting system was then placed under a nitrogen protective atmosphere, and under stirring conditions, a 10% praseodymium chloride solution was added dropwise to the system at a molar ratio of rare earth compound (praseodymium chloride) to 5-hydroxy-2-nitrobenzoic acid of 1:1. After the addition was complete, the system was heated to 80°C and reacted at a constant temperature for 30 min to obtain a chelate reaction solution of rare earth ions and 5-hydroxy-2-nitrobenzoic acid, which was then set aside.

[0045] (2) The chelate reaction solution was cooled to 50°C and kept at that temperature. Then, a polycarboxylate superplasticizer was added to it, with a mass ratio of 15:2 to the 5-hydroxy-2-nitrobenzoic acid. The reaction was then stirred at 200 r / min for 60 min at the 50°C temperature to obtain PCE-5-hydroxy-2-nitrobenzoic acid-RE. 3+ Ternary coordination complex reaction solution, ready for use.

[0046] (3) After cooling the ternary coordination complex reaction solution to room temperature, 2-phosphonobutane-1,2,4-tricarboxylic acid is added to it, with a mass ratio of 2-phosphonobutane-1,2,4-tricarboxylic acid to 5-hydroxy-2-nitrobenzoic acid of 1:1.5. The mixture is then stirred at 150 r / min for 40 min. After this, polycarboxylic acid superplasticizer is added again, with a mass ratio of 2-hydroxy-2-nitrobenzoic acid to 5-hydroxy-2-nitrobenzoic acid of 12:2. Finally, 105 times the mass of water is added to the resulting system for dilution, and the mixture is stirred until homogeneous to obtain the modified grinding aid (e.g., ...). Figure 3 (As shown).

[0047] Performance testing: The modified grinding aid prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in Table 3 below.

[0048] Table 3

[0049] Example 4: A method for preparing a modified grinding aid to reduce the hardness of cement particles, comprising the following steps: (1) 5-Hydroxy-2-nitrobenzoic acid and water were mixed at a mass ratio of 1:80 and stirred to form a dispersion. Then, 0.1 mol / L NaOH solution was added to adjust the pH of the suspension to 5. The resulting system was then placed under a nitrogen protective atmosphere, and a 6.25% lanthanum nitrate solution was added dropwise to the system under stirring at a molar ratio of rare earth compound (lanthanum nitrate) to 5-hydroxy-2-nitrobenzoic acid of 1:2. After the addition was complete, the system was heated to 70°C and reacted at a constant temperature for 45 min to obtain a chelate reaction solution of rare earth ions and 5-hydroxy-2-nitrobenzoic acid, which was then set aside.

[0050] (2) The chelate reaction solution was cooled to 45°C and kept at that temperature. Then, a polycarboxylate superplasticizer was added to it, with a mass ratio of 18:0.5 between the superplasticizer and the 5-hydroxy-2-nitrobenzoic acid. The mixture was then stirred at 300 r / min for 45 min at the 45°C temperature to obtain PCE-5-hydroxy-2-nitrobenzoic acid-RE. 3+ Ternary coordination complex reaction solution, ready for use.

[0051] (3) After cooling the ternary coordination complex reaction solution to room temperature, add polycarboxylate superplasticizer to it, with a mass ratio of 9:1 between the superplasticizer and the 5-hydroxy-2-nitrobenzoic acid. Finally, dilute the resulting system with 100 times its mass of water, stir evenly, and the modified grinding aid (such as...) is obtained. Figure 4 (As shown).

[0052] Performance testing: The modified grinding aid prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in Table 4 below.

[0053] Table 4

[0054] Example 5: A method for preparing a modified grinding aid to reduce the hardness of cement particles, comprising the following steps: (1) Salicylic acid and water were mixed at a mass ratio of 1:80 and stirred to form a dispersion. Then, 0.1 mol / L NaOH solution was added to adjust the pH of the suspension to 5. The resulting system was then placed under a nitrogen protective atmosphere, and a 6.25% lanthanum nitrate solution was added dropwise to the system under stirring at a molar ratio of rare earth compound (lanthanum nitrate) to salicylic acid of 1:2. After the addition was complete, the system was heated to 70°C and reacted at a constant temperature for 45 min to obtain a rare earth-salicylic acid chelate reaction solution for later use.

[0055] (2) The chelate reaction solution was cooled to 45°C and kept at that temperature. Then, a polycarboxylate superplasticizer was added to it at a mass ratio of 18:0.5 to the salicylic acid. The mixture was then stirred at 300 r / min for 45 min at the 45°C temperature to obtain PCE-salicylic acid-RE. 3+ Ternary coordination complex reaction solution, ready for use.

[0056] (3) After cooling the ternary coordination complex reaction solution to room temperature, 3,4-dihydroxyphenylacetic acid is added to it at a mass ratio of 1:0.8 to the salicylic acid. The mixture is then stirred at 200 r / min for 30 min. After this, polycarboxylate superplasticizer is added again at a mass ratio of 9:1 to the salicylic acid. Finally, 100 times its mass of water is added to the resulting system for dilution, and the mixture is stirred until homogeneous to obtain the modified grinding aid (e.g., ...). Figure 5 (As shown).

[0057] Performance testing: The modified grinding aid prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in Table 5 below.

[0058] Table 5

[0059] Example 6: A method for preparing a modified grinding aid to reduce the hardness of cement particles, comprising the following steps: (1) Mix 5-hydroxy-2-nitrobenzoic acid and water at a mass ratio of 1:80 and stir to form a dispersion. Then add 0.1 mol / L NaOH solution to adjust the pH of the suspension to 5 and set aside.

[0060] (2) The suspension was cooled to 45°C and kept at that temperature. Then, a polycarboxylate superplasticizer was added to it, with a mass ratio of 18:0.5 between the superplasticizer and the 5-hydroxy-2-nitrobenzoic acid. The mixture was then stirred at 300 r / min for 45 min at the 45°C temperature to obtain PCE-5-hydroxy-2-nitrobenzoic acid-RE. 3+ Ternary coordination complex reaction solution, ready for use.

[0061] (3) After cooling the ternary coordination complex reaction solution to room temperature, 3,4-dihydroxyphenylacetic acid is added to it, with a mass ratio of 3,4-dihydroxyphenylacetic acid to 5-hydroxy-2-nitrobenzoic acid of 1:0.8. Then, the mixture is stirred at 200 r / min for 30 min. After the reaction is complete, polycarboxylate superplasticizer is added again, with a mass ratio of 3,4-dihydroxyphenylacetic acid to 5-hydroxy-2-nitrobenzoic acid of 9:1. Finally, 100 times the mass of water is added to the obtained system for dilution, and the mixture is stirred evenly to obtain the modified grinding aid (e.g., Figure 6 (As shown).

[0062] Performance testing: The modified grinding aid prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in Table 6 below.

[0063] Table 6

[0064] Example 7: A method for preparing a modified grinding aid to reduce the hardness of cement particles, comprising the following steps: (1) 5-Hydroxy-2-nitrobenzoic acid and water were mixed at a mass ratio of 1:70 and stirred to form a dispersion. Then, 0.1 mol / L NaOH solution was added to adjust the pH of the suspension to 4. The resulting system was then placed under a nitrogen protective atmosphere, and 10% cerium nitrate solution was added dropwise to the system under stirring at a molar ratio of rare earth compound (cerium nitrate) to 5-hydroxy-2-nitrobenzoic acid of 1:1.5. After the addition was complete, the system was heated to 60°C and reacted at a constant temperature for 60 min to obtain a chelate reaction solution of rare earth ions and 5-hydroxy-2-nitrobenzoic acid, which was then set aside.

[0065] (2) The chelate reaction solution was cooled to 40°C and kept at that temperature. Then, a polycarboxylate superplasticizer was added to it, with a mass ratio of 5-hydroxy-2-nitrobenzoic acid to 5:0.3. The mixture was then stirred at 400 r / min for 30 min at the 40°C temperature to obtain PCE-5-hydroxy-2-nitrobenzoic acid-RE. 3+ Ternary coordination complex reaction solution, ready for use.

[0066] (3) After cooling the ternary coordination complex reaction solution to room temperature, a coordinating organic compound (composed of protocatechuic acid and 3,4-dihydroxyphenylacetic acid in a mass ratio of 1:2) is added to it, with a mass ratio of 1:0.2 to the 5-hydroxy-2-nitrobenzoic acid. The mixture is then stirred at 300 r / min for 20 min. Finally, 95 times its mass of water is added to the resulting system for dilution, and the mixture is stirred until homogeneous to obtain the modified grinding aid (e.g., ...). Figure 7 (As shown).

[0067] Performance testing: The modified grinding aid prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in Table 7 below.

[0068] Table 7

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified grinding aid to reduce the hardness of cement particles, characterized in that, Includes the following steps: (1) 5-hydroxy-2-nitrobenzoic acid is added to water to form a dispersion. Then, an alkaline solution is added to adjust the pH of the dispersion. Rare earth compound aqueous solution is added under stirring. After the reaction is completed, the reaction is heated to obtain a chelate reaction solution of rare earth ions and 5-hydroxy-2-nitrobenzoic acid for later use. (2) After cooling the chelate reaction solution, add the polycarboxylate superplasticizer, and then stir the reaction. After completion, PCE-5-hydroxy-2-nitrobenzoic acid-RE is obtained. 3+ Ternary coordination complex reaction solution, ready for use; (3) After cooling the ternary coordination complex reaction solution to room temperature, add an organic compound containing at least two coordination functional groups to it and then stir the reaction. After the reaction is completed, add polycarboxylate superplasticizer and mix well. Then dilute the resulting system with water to obtain the modified grinding aid. In step (1), the rare earth compound includes at least one of the following: nitrates or chlorides of lanthanum, cerium, praseodymium, neodymium, and yttrium; In step (1), the mass ratio of 5-hydroxy-2-nitrobenzoic acid to water is 1:70~85; In step (1), the molar ratio of the rare earth compound to 5-hydroxy-2-nitrobenzoic acid is 1:1~2; In step (2), the mass ratio of the polycarboxylate superplasticizer to 5-hydroxy-2-nitrobenzoic acid is 5~18:0.3~2; In step (3), the mass ratio of the organic compound to 5-hydroxy-2-nitrobenzoic acid is 1:0.2~1.5; In step (3), the mass ratio of the polycarboxylate superplasticizer to 5-hydroxy-2-nitrobenzoic acid is 5~12:0.3~2; In step (3), the organic compound includes at least one of protocatechuic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and 3,4-dihydroxyphenylacetic acid.

2. The method for preparing the modified grinding aid for reducing the hardness of cement particles according to claim 1, characterized in that, In step (1), the pH value of the dispersion is adjusted to 4~5.

5.

3. The method for preparing the modified grinding aid for reducing the hardness of cement particles according to claim 1, characterized in that, In step (1), the alkaline solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, ammonia water, sodium carbonate solution, and sodium bicarbonate solution.

4. The method for preparing the modified grinding aid for reducing the hardness of cement particles according to claim 1, characterized in that, In step (1), the heating reaction is carried out at a temperature of 60-80°C for 30-60 minutes.

5. The method for preparing the modified grinding aid for reducing the hardness of cement particles according to claim 1, characterized in that, In step (2), the chelate reaction solution is cooled to 40~50°C.

6. The method for preparing the modified grinding aid for reducing the hardness of cement particles according to claim 1, characterized in that, In step (2), the temperature of the stirring reaction is 40~50℃, the stirring rate is 200~400r / min, and the reaction time is 30~60min.

7. The method for preparing the modified grinding aid for reducing the hardness of cement particles according to claim 1, characterized in that, In step (3), the stirring reaction time is 20-40 min and the stirring rate is 150-300 r / min.

8. The method for preparing the modified grinding aid for reducing the hardness of cement particles according to any one of claims 1-7, characterized in that, In step (3), 95 to 105 times the mass of water is added to the system for dilution.

9. The application of the modified grinding aid obtained by the preparation method according to any one of claims 1-8 in the preparation of cement clinker powder includes the following steps: mixing the modified grinding aid with cement clinker and then grinding it to obtain cement clinker powder.

10. The application according to claim 9, characterized in that, The modified grinding aid is 0.1-0.5% of the cement clinker mass.

Images